The incidence, predictors and outcomes of QTc prolongation in critically ill patients

Purpose: To study the incidence, predictors and outcomes of QTc prolongation (≥500 ms) during ICU admission. Methods: Prospective observational study of patients admitted to a tertiary ICU during a two-month period. We obtained daily data on QTc intervals and arrhythmias from ICU monitors. We performed univariate and multivariable analyses to compare patients who did or did not experience QTc prolongation. Results: Of the 257 patients, 93 (36.2%) developed ≥1 episode of QTc ≥500 ms. Such patients had higher APACHE II scores (p < .001), received more QT-prolonging medications (p = .002), and more frequently developed non-sustained (<8 beats, p = .007) and sustained ventricular tachycardia (≥8 beats; p < .001). However, after adjustment for confounders, there was no independent association between QTc duration and odds of ventricular tachyarrhythmia (OR = 0.921 [0.593–1.431], p = .715). Moreover, 98% of ventricular tachyarrhythmias resolved spontaneously. Patients with QTc prolongation had longer ICU (p < .001) and hospital length-of-stay (p = .002), and greater ICU (p = .030) and in-hospital mortality (p = .015). No patient experienced sustained Torsades de Pointes or died from ventricular arrhythmia. Conclusions: A QTc ≥500 ms likely represents a marker of illness severity modulated by several risk factors, and carries no independent association with clinically-significant ventricular tachyarrhythmias. Thus, cessation of QT-prolonging medications to prevent arrhythmias may lack clinical benefit.